Question about my mill.

[TomG]

Tram is defined as the perpendicularity of the spindle to the table. It is checked by swinging an indicator across the surface of the table, or ground parallels laying on the table. If the head is in tram, the indicator should read the same at 12:00, 3:00, 6:00 and 9:00 as it is swung. The variation you are measuring by running the table under an indicator presumably held in the spindle is something different, most likely wear on the gibs or ways of the X axis. Try tightening the gib and see if it improves. If not, the ways are likely worn and will have to be scraped or re-machined to regain the lost precision.

Tom